Over the past generation, virtualization of computer processors has become commonplace. This virtualization involves time slicing of the virtual processors or machines between physical processors. In such virtual processor environments wherein multiple user computers, i.e. client devices, are connected to each virtual processor platform that provides a plurality of physical processors respectively connected to these, power management is important. This is particularly the case with current technology of multicore processors on a single integrated circuit chip, e.g. dual core chips. These multicore processors, when operating effectively, do reduce power consumption and, consequently, wasted heat. However, such multicore processors require tighter power management so as obtain maximum overall processor power per watt in a virtualized environment. It is consequently important to constrain power at all levels.
In the current state of virtualization technology, the multicore processors on a particular platform are controlled by a hypervisor so that a plurality of computer applications, concurrently running respectively on client computer/devices provide threads that in turn are run on the virtual logical processors with each logical processor being represented by a partition wherein each partition has an allocation known as an entitlement to at least a fraction of a core (physical processor). This entitlement is equivalent to a guarantee that the system or power management system administrator provides to a partition. This entitlement assures the particular partition that its MIPS (millions of instructions per second) will not be reduced without the agreement of the user or administrator of the partition. This presents problems when power efficiency management results in one or more partitions requesting a reduction in power. Since the micro-partitions share entitlement in the same core, as well as multicores sharing the same substrate, or share entitlement in a shared pool of multicores that may be spread out on multiple substrates (nodes), non-requesting partitions will be affected by such reductions in power of the shared processors. Currently, all micro-partitions may be particularly affected by requests for power reduction in selected micro-partitions.